Regular network connection failure of a Kafka broker in a 3 broker cluster in OpenShift

Question

For reasons unknown and often several times a week in Production and Test, we cannot communicate with a Kafka broker, and this message repeats in the log: WARN Connection to node nnnn could not be established. Broker may not be available. (org.apache.kafka.clients.NetworkClient)

Strangely this in turn prevents Kafka working (We cannot Produce/Consume).

OpenShift doesn't recognize it's not working, and Kafka doesn't recognize it either.

I am about to add a Livenessprobe to the YAML to restart the Pod if the command in a Broker container is not executed, but we'd like to find the root cause naturally.

If I use the Curl url:hostport command from another Broker or Zookeeper node, you can get a reply from all other Brokers and Zookeepers. Yet Curl to the Kafka node that has "failed" returns "Could not resolve host ...", even though I can go into OpenShift and use the Terminal. I cannot find any other errors in the logs.

I don't know if this is a Kafka or OpenShift/Kubernetes issue.

If anyone else has had this and resolved it, I'd be grateful for some pointers.

Answer 1

I had such an error when configuring kafka. It's due to the brokers not able to communicate among them.

Here a snippet of my StatefulSet (I use kubernetes):

apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
  name: kafka
spec:
  serviceName: kafka
  replicas: 1
  template:
    metadata:
      labels:
        app: kafka
    spec:
      affinity:           
        podAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
             - weight: 1
               podAffinityTerm:
                 labelSelector:
                    matchExpressions:
                      - key: "app"
                        operator: In
                        values:
                        - zookeeper
                 topologyKey: "kubernetes.io/hostname"
      terminationGracePeriodSeconds: 300
      containers:
      - name: kafka
        imagePullPolicy: IfNotPresent
        image: your_kafka_image
        resources:
          requests:
            memory: 500Mi
            cpu: 500m
        ports:
        - containerPort: 9092
          name: server
        command:
        - sh
        - -c
        - "exec kafka-server-start.sh /opt/kafka/config/server.properties --override broker.id=${HOSTNAME##*-} \
          --override listeners=PLAINTEXT://:9092 \
          --override zookeeper.connect=zookeeper-0.zookeeper:2181 \
          --override log.dirs=/var/lib/kafka \
          --override auto.create.topics.enable=true \
          --override auto.leader.rebalance.enable=true \
          --override background.threads=10 \
          --override compression.type=producer \
          --override delete.topic.enable=false \
          --override leader.imbalance.check.interval.seconds=300 \
          --override leader.imbalance.per.broker.percentage=10 \
          --override log.flush.interval.messages=9223372036854775807 \
          --override log.flush.offset.checkpoint.interval.ms=60000 \
          --override log.flush.scheduler.interval.ms=9223372036854775807 \
          --override log.message.format.version=1.0 \
          --override log.retention.bytes=-1 \
          --override log.retention.hours=168 \
          --override log.roll.hours=168 \
          --override log.roll.jitter.hours=0 \
          --override log.segment.bytes=1073741824 \
          --override log.segment.delete.delay.ms=60000 \
          --override message.max.bytes=1000012 \
          --override min.insync.replicas=1 \
          --override num.io.threads=8 \
          --override num.network.threads=3 \
          --override num.recovery.threads.per.data.dir=1 \
          --override num.replica.fetchers=1 \
          --override offset.metadata.max.bytes=4096 \
          --override offsets.commit.required.acks=-1 \
          --override offsets.commit.timeout.ms=5000 \
          --override offsets.load.buffer.size=5242880 \
          --override offsets.retention.check.interval.ms=600000 \
          --override offsets.retention.minutes=1440 \
          --override offsets.topic.compression.codec=0 \
          --override offsets.topic.num.partitions=50 \
          --override offsets.topic.replication.factor=1 \
          --override offsets.topic.segment.bytes=104857600 \
          --override queued.max.requests=500 \
          --override quota.consumer.default=9223372036854775807 \
          --override quota.producer.default=9223372036854775807 \
          --override request.timeout.ms=30000 \
          --override socket.receive.buffer.bytes=102400 \
          --override socket.request.max.bytes=104857600 \
          --override socket.send.buffer.bytes=102400 \
          --override unclean.leader.election.enable=true \
          --override broker.id.generation.enable=true \
          --override connections.max.idle.ms=600000 \
          --override controlled.shutdown.enable=true \
          --override controlled.shutdown.max.retries=3 \
          --override controlled.shutdown.retry.backoff.ms=5000 \
          --override controller.socket.timeout.ms=30000 \
          --override default.replication.factor=1 \
          --override fetch.purgatory.purge.interval.requests=1000 \
          --override group.max.session.timeout.ms=300000 \
          --override group.min.session.timeout.ms=6000 \
          --override inter.broker.protocol.version=1.0 \
          --override log.cleaner.backoff.ms=15000 \
          --override log.cleaner.dedupe.buffer.size=134217728 \
          --override log.cleaner.delete.retention.ms=86400000 \
          --override log.cleaner.enable=true \
          --override log.cleaner.io.buffer.load.factor=0.9 \
          --override log.cleaner.io.buffer.size=524288 \
          --override log.cleaner.io.max.bytes.per.second=1.7976931348623157E308 \
          --override log.cleaner.min.cleanable.ratio=0.5 \
          --override log.cleaner.min.compaction.lag.ms=0 \
          --override log.cleaner.threads=1 \
          --override log.cleanup.policy=delete \
          --override log.index.interval.bytes=4096 \
          --override log.index.size.max.bytes=10485760 \
          --override log.message.timestamp.difference.max.ms=9223372036854775807 \
          --override log.message.timestamp.type=CreateTime \
          --override log.preallocate=false \
          --override log.retention.check.interval.ms=300000 \
          --override max.connections.per.ip=2147483647 \
          --override num.partitions=1 \
          --override producer.purgatory.purge.interval.requests=1000 \
          --override replica.fetch.backoff.ms=1000 \
          --override replica.fetch.min.bytes=1 \
          --override replica.fetch.max.bytes=1048576 \
          --override replica.fetch.response.max.bytes=10485760 \
          --override replica.fetch.wait.max.ms=500 \
          --override replica.high.watermark.checkpoint.interval.ms=5000 \
          --override replica.lag.time.max.ms=10000 \
          --override replica.socket.receive.buffer.bytes=65536 \
          --override replica.socket.timeout.ms=30000 \
          --override reserved.broker.max.id=1000 \
          --override zookeeper.session.timeout.ms=6000 \
          --override zookeeper.set.acl=false "
        env:
        - name: KAFKA_HEAP_OPTS
          value : "-Xmx512M -Xms512M"
        - name: KAFKA_OPTS
          value: "-Dlogging.level=WARN"
        - name: ZOOKEEPER_CONNECT
          value: "zookeeper"
        volumeMounts:
        - name: data
          mountPath: /var/lib/kafka
        readinessProbe:
          exec:
           command:
            - sh
            - -c
            - "/opt/kafka/bin/kafka-broker-api-versions.sh --bootstrap-server=localhost:9092"
      securityContext:
        runAsUser: 1000
        fsGroup: 1000
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      resources:
        requests:
          storage: 1Gi
      accessModes:
      - ReadWriteOnce
      storageClassName: kafka-class

The option --override zookeeper.connect=zookeeper-0.zookeeper:2181 is very important and there you need to list all zookeeper nodes.

Because I defined a service for Zookeeper and only one StatefulSet for zookeeper, inside the abode option I wrote zookeeper-0.zookeeper

If you have more, list them all.

My previous posts are at:

• Kafka + Zookeeper: Connection to node -1 could not be established. Broker may not be available

• Kubernetes service not working as expected with kafka

You may find useful info in them. I hope this helps.